1. The Field Of The Invention
The present invention broadly relates to the operation of an internal combustion engine on an admixture of air and fuel vapor generated from a volatile normally liquid fuel. In one of its more specific aspects, the invention is concerned with improved apparatus for generating fuel vapor from a volatile normally liquid fuel for an internal combustion engine. In another of its aspects, the invention relates to improved apparatus for safely handling and controlling the fuel vapor thus generated, and utilizing the same in the operation of the internal combustion engine. The invention is additionally concerned with a novel method of generating vapor of a volatile liquid fuel and operating an internal combustion engine therewith. The method is also useful in modifying a conventional internal combustion engine including a prior art carburetor for preparing a fuel charge from a volatile normally liquid fuel, whereby the said internal combustion engine following modification is capable of operating more efficiently and with lower exhaust emissions.
2. The Prior Art
Conventional gasoline powered internal combustion engines include a carburetor into which the gasoline is introduced and atomized, and atmospheric air is introduced simultaneously and admixed with the atomized gasoline. The liquid gasoline is not completely vaporized at the time of combustion and a substantial amount exists in the form of finely divided droplets which do not burn completely. As a result, prior art internal combustion engines utilizing a conventional carburetor for preparation of an air-liquid fuel admixture to be combusted are very inefficient. They are also further characterized by unacceptable levels of undesirable exhaust emissions, such as carbon monoxide and uncombusted hydrocarbons.
It has been recognized heretofore that the efficiency of internal combustion engines of the aforementioned type could be improved and the exhaust emissions reduced by vaporizing the liquid fuel, and then admixing the resultant fuel vapor with atmospheric air to prepare the charge to be combusted. However, the prior art systems available for generating the fuel vapor and thereafter utilizing the same in the operation of an internal combustion engine have not been entirely satisfactory.
For instance, the prior art systems for generating fuel vapor often involve heating the liquid fuel with hot exhaust gases, or other sources of high temperature, to thereby evaporate the same at an elevated temperature which may approach or reach the boiling point. The resultant hot fuel vapor has a relatively low volumetric efficiency per unit of volume when admixed with atmospheric air in the preparation of the charge to be combusted. This reduces the amount of power developed by the internal combustion engine as compared with the theoretical amount of power available when using cool fuel vapors in preparing the charge. The use of elevated temperature in evaporating the liquid fuel also creates an unacceptable fire and/or explosion hazard which endangers the lives of occupants in an automotive vehicle powered by the internal combustion engine. Additionally, the hot fuel vapor is unstable and tends to form fog-like finely divided liquid fuel droplets. These fuel droplets remain suspended in the fuel vapor and fail to combust completely, and thus reduce efficiency and increase exhaust emissions. The instability of the hot fuel vapor also results in liquid fuel being deposited on surfaces in contact therewith. The surfaces wetted with the liquid fuel create a fire hazard, and inasmuch as the liquid fuel deposited thereon is not available for combustion, the overall efficiency is further reduced.
In other systems for generating fuel vapor proposed heretofore, atmospheric air is bubbled through the liquid fuel, and/or the atmospheric air is directed directly onto the liquid fuel surface. In some instances, these systems require means for heating the liquid fuel and/or the air to a sufficiently elevated temperature to assure evolution of sufficient fuel vapor for operating the internal combustion engine. Also, these systems introduce sufficient air to result in an explosive mixture being produced for operating the internal combustion engine. Thus, an unacceptable fire and explosion hazard is created.
In view of the foregoing, it is apparent that the prior art systems for generating fuel vapor, handling and/or controlling the resultant fuel vapor, and utilizing the same in the operation of an internal combustion engine have not been entirely satisfactory. The present invention overcomes the deficiencies of the prior art and provides an entirely satisfactory method and apparatus for generating vapor of a volatile liquid fuel and operating an internal combustion engine therewith.